Healthy ears emit sounds that are used to screen newborn hearing

Evidence

The active role of the outer hair cells is firmly established. Indeed, the contractions of the outer hair cells create sound that can be heard outside the ear: so-called otoacoustic emissions, which were first demonstrated experimentally by David Kemp in 1978. If a click is sent into the ear, a return signal is received, courtesy of the outer hair cells. Damaged ears may not have this active feedback mechanism. Such otoacoustic emissions have become a standard way to detect severe middle ear hearing loss. Newborn babies are now routinely checked; they are presented with clicking sounds, and there should be a response sound coming out of their ears. — Eric J. Heller, Why You Hear What You Hear- An…, 1961

Categorization

• CANDY: Newborn hearing tests rely on the ear literally broadcasting a return click — the ear is an active sound-maker, not a passive receiver.
• SHARE: Send to anyone in pediatrics or audiology: the otoacoustic emission screening mechanism behind routine newborn hearing checks.
• ADDENDUM: Could bolster ‘Grafting & Growth’ style essays only loosely, but mainly enriches the reader’s answer on mechanisms of hearing.